1. Field of the Invention
The present invention relates to a valve for an aerosol device, and more specifically, but not exclusively, to a valve for an aerosol device for a metered dose inhaler.
2. The Prior Art
The term aerosol is considered to encompass all types of pressurized containers used for delivery of aerosolized products meant for a variety of medical and non-medical applications including, but not limited to, drugs, cosmetics (deodorants, hair sprays, hair mousses, shaving creams), perfumes, air fresheners, insect repellents, cleaning agents, paints, lubricants and the like. Aerosol devices may deliver aerosolized, ingredients in an uneven or continuous manner delivering varying quantities per actuation, or in a uniform manner, delivering predetermined identical quantities, or doses, per actuation.
A metered dose inhaler is a dispenser designed to deliver a specific dose of medication to a user with each usage.
Typically, aerosol devices comprise a container and a valve crimped on the container. The valve is fitted to the body of the container by crimping a valve ferrule against the body of the container with an intermediate seal made of an elastomeric material compressed between the body and the ferrule. The process of positioning a valve in place and crimping around it to form a seal and close the container is time consuming. Aerosol devices produced in this way are prone to leakages resulting from improper sealing of the valve and the body of the container. Aside from the difficulty in obtaining an efficient seal, the step of crimping involves a considerable amount of production time during the manufacture of such devices. Frequent testing of the devices must be conducted throughout the manufacturing process to ensure that leaks are not present. This all requires extra skilled man-power and machinery, thereby increasing the overall cost and time required for the production.
The problem of leaks is especially significant in the case of medicinal aerosol formulations. In medicinal aerosol formulations it is important to ensure that an appropriate concentration of the drug in the container is maintained throughout the entire usage period. Leakage of the propellants in such devices can lead to non-uniform and unpredictable drug delivery, which is a serious problem with these devices.
It is common in many aerosol devices to use thermoplastic elastomers as an additional means to obtain a more effective seal. However, in aerosols meant for medicinal purposes this technique has, further drawbacks. Contact of the medication with an elastomer greatly increases the chances of drug contamination through the process of leaching. If the elastomeric elements are not incorporated, in an effort to avoid this problem, the sealing of the aerosol device through crimping is compromised, leading to increased leakage problems as discussed above.
Numerous attempts have been made to make leakage resistant aerosol devices. Various known aerosol devices incorporate an intermediate seal, either in the form of a ferrule gasket placed and compressed between the top edge of the body of the container and the opposing surface of the ferrule gasket, or of an O-ring placed around the exterior of the body of the container and compressed between the body of the container and an annular flange of the valve ferrule. Other approaches include incorporating gaskets made up of material of varying durometer values, in an attempt to achieve more effective sealing. However, the problems discussed above still remain.
It would be beneficial if a valve assembly could be provided for an aerosol device which enabled the aerosol device to be more easily sealed, while also allowing more efficient production of the aerosol device.
Conventional aerosol devices have a number of further disadvantages. In many cases, due to the shape of the container used, it is not possible for the container to dispense every last drop of a substance to be delivered. This is wasteful in all applications, but is most significant where a medicament is to be delivered by the aerosol device. Canisters for use with metered dose inhalers are designed to deliver a certain number of controlled doses of medicament to a user. The devices are commonly employed in inhaler apparatus to treat asthma and similar complaints. Since in existing canisters there is often a quantity of the medicament which cannot be delivered, the container is routinely over-filled (in some cases by up to fifteen percent). This not only increases the amount of medicament, propellant and the size of container required for a given number of doses, but also complicates the calculation of the amount of medicament required. If one could be sure of complete exhaustion of a container during use, then less medicament could be used with a smaller container, the filling of which would be simplified because only the number of doses and size of each dose would need to be known in order to determine the size/volume of container required.
It is an object of the present invention to provide a valve for an aerosol device which also serves as a closure for the aerosol device. It is a related object of the present invention to provide a valve assembly for an aerosol device which allows for nearly complete exhaustion of the substance contained in the aerosol device.